Modeling of building thermal behavior needs effective tools. This is particularly true when conduction of heat through walls and/or slabs has to be computed. This paper represents a framework of a new methodology in Building energy simulation. Hence, it will give emphasis to a new modeling approach for solving the transient heat conduction equation in finite medium with different boundary conditions in order to apply it for modeling heat transfer in the different elements of buildings structure. The developed modeling approach is performed using the Bond graph technique, a graphical modeling language which is perfectly accustomed with dynamic systems involving energy transfer. With this original model, two transient heat conduction problems corresponding to the most practical cases in building envelope, such a heat transfer through vertical walls, roofs and slabs, have been treated. The validation procedure consists of comparing the results obtained with this model with analytical solution. It has shown very good agreement between measured data and Bond Graphs model simulation. The Bond Graphs technique is then used to model the building dynamic thermal behavior over a single zone building structure and compared with a set of experimental data. An evaluation of indoor temperature was carried out in order to check our Bond Graphs model